Materials Literature
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A general class of models is introduced which relate the motion of a phase boundary to properties of the local interfacial geometry. These systems can undergo successive destabilizations as they grow, possibly giving rise to nonequilibrium spatial patterns. This formalism has applications to a wide variety of physical…
For pt.II see ibid., vol.16, p.2455 (1983). The temperature and pressure dependences of the elastic and strain-related properties of the 'pseudo-proper' ferroelectric material BiVO 4 have been determined using mean-field theory. In the tetragonal paraelastic phase the elastic constants c 11 -c 12 , c 66 and c 16 are a…
For pt.IV see ibid., vol.16, p.5119 (1983). Measurements of the Bi 3+ displacement and the primary and secondary spontaneous strains in the ferroelastic material BiVO 4 have been made as a function of temperature by single-crystal X-ray diffraction. The results are discussed using both macroscopic and microscopic mean…
For pt.V see ibid., vol.16, p.5127 (1983). The relationship between the domain wall orientation and the spontaneous strain in ferroelastics is discussed, with particular reference to the W' walls in BiVO 4 . The microscopic, wall-defining property is shown to be the coherence of the lattices of the twin components. Th…
The effect of doping of Tl upon thermoluminescence, its emission and optical absorption in flux grown BaFCl crystals is investigated. Besides an increase in luminescence output, X/γ-irradiations of BaFCl: Tl crystals produce three additional glow peaks at 450,465, and 500 K and a TL emission spectrum at 460 nm. Optica…
The grain cathodoluminescence (CL) properties of bariumtitannte ceramics, sintered at, different oxygen partial pressures are systematically investigated. The spectra are found to be composed of different bands, the intensities of which depends strongly on the specimen temperature and on the oxygen partial pressure of…
In the analysis of the thermoluminescence glow curves, and in particular when applied to TL dosimetry and TL dating of archaeological and geological samples, a first order behaviour of the peaks involved is usually implicitly assumed. In this work the TL response for second order kinetics is described and shown that t…
Studies of the structural phase transition of CsPbCl3, are carried out, using X-ray and neutron diffraction, NQR and Raman scattering below room temperature. It is confirmed that there is a second-order transition at about 200 K (TC4). From the structural analysis, it is determined that, at room temperature, the struc…
The intensities of photoluminescence lines D1 through D4 and also of the background component that are characteristic in a dislocated silicon crystal are measured as a function of the temperature. All of them become weaker as the temperature is raised. Such behaviour is interpreted in a quantitative way with the model…
We report the first observation of a pressure-induced phase transition in LiI${\mathrm{O}}_{3}$. A new phase appears when $\ensuremath{\beta}\ensuremath{-}\mathrm{Li}\mathrm{I}{\mathrm{O}}_{3}$ is compressed hydrostatically at room temperature, beyond 50 kbar. This is a reversible first-order transition with negligibl…
The thermal conductivity of an anharmonic crystal containing randomly distributed substitutional defects due to impurity-phonon scattering is theoretically investigated with the use of the method of double-time thermal Green's functions and the Kubo formalism considering all the terms, i.e., diagonal, nondiagonal, cub…
Polycrystalline ${\mathrm{H}}_{2}$S${\mathrm{O}}_{4}$ and ${\mathrm{H}}_{2}$Se${\mathrm{O}}_{4}$ were studied by powder neutron-diffraction techniques at temperatures near the melting points and at 10 K. This work was undertaken to determine hydrogen positions and to search for order-disorder transitions in the hydrog…
The kinetics of hydrogen absorption by polycrystalline α-zirconium metals has been investigated by the use of spherical specimens in the pressure range 2×10−5–1×101 Pa and in the temperature range 673–1073 K. The experimental results are reasonably explained on the basis of the model in which the process is assumed to…
$n$-type, ${10}^{13}$ and 2 \ifmmode\times\else\texttimes\fi{} ${10}^{15}$ ${\mathrm{cm}}^{\ensuremath{-}3}$ doped germanium has been irradiated with \ensuremath{\sim} 1-MeV electrons at liquid-helium and room temperatures. With the use of transient-capacitance spectroscopy, six electron traps and one hole trap were o…
We have studied steady-state heat flow in a two-dimensional crystal by the method of molecular dynamics. The model system contains 1000 particles on a triangular lattice interacting via the Lennard-Jones potential. The system is 50 unit cells long and 10 unit cells wide. We find that the thermal conductivity $\ensurem…
The steady-state velocity of a planar liquid-solid interface is predicted by calculating the free energy dissipated by irreversible processes at the interface and equating it to the available driving free energy. A solute drag term and an intrinsic interfacial mobility term are included in the dissipation calculations…
We present experimental determinations of the cross section for photoionization for $4d$ and $5d$ valence states in transition and noble metals and at the interfaces that these metals form with elemental semiconductors (group IV) in the photon-energy range $h\ensuremath{\nu}=70\ensuremath{-}200$ eV. A description of t…
In strict analogy with the case of silicon, the Hall-coefficient factor of holes in natural diamond is found to be systematically less than unity in the range of temperature $100<T<1000$ K investigated here. A microscopic interpretation is shown to provide information on the reliability of a different set of inv…
A dynamic bond percolation model is defined and studied. The model is intended to describe diffusion of small particles (ions, electrons) in a medium which is statistically disordered (as in ordinary bond percolation), but which is also undergoing dynamic rearrangement processes on a timescale short compared to the ob…
The first-order Raman spectra of vitreous Si${\mathrm{O}}_{2}$ have been studied as a function of sample fictive temperature ${T}_{F}$ for $900\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}\ensuremath{\le}{T}_{F}\ensuremath{\le}1550\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$. Three observations were made: (1) The br…